Hydraulic load arm



Oct. 23, 1956 G. EHMANN 2,758,018 Y HYDRAULIC LOAD ARM Filed July 7, 1952 ///////////1.' [III llllllllI/ll' nnnnnnnu 56 INVENTOR. LESLIE G. EHMANN ATTORNEYS United States Patent C) HYDRAULIC LOAD ARM Leslie G. Ehmann, Portland, Oreg., assignor to Hyster Company, Portland, Greg., a corporation of Oregon Application July 7, 1952, Serial No. 297,540.

Claims. (Cl. 294-63) The present invention relates to material handling apparatus and more particularly to a loadv engaging arm for apparatus of a type having a pair of arms adapted tro grip a load therebetween for lifting the same.

The use lof grip type load arms on material handling devices, such as lift trucks, is convenient since materials may be lifted thereby and transported without the use `of pallets. As will be apparent, arms of different types and shapes may be necessary to handling various types of loads, and to increase their versatility it is desirable that lift trucks be so constructedV that diiferent` types of load arms may be readily interchanged thereon. Grip type load arms have been designed heretofore for handling irregularly surfaced articles such as brick -stacksand the like, and pro-vided with load engaging portions backed' by uid filled means so that the portionsk can accommodate themselves to the irregularities in the. load surface and more or less equitably distribute the force exerted by the arms over the entire engaged surface yof. the load. Such arrangements as have been provided heretofore have been unsatisfactory, some because they all have been defective in that in the event of the collapse of the fluid filled means or in the event of bottoming of one or more of'the load engaging portions, a part or all ofthe load would be dropped.

lt is the principal object of the present invention, therefore, to provide a new and improved grip type loadV arm which overcomes the above disadvantages and'v in particular will not drop a part or all of the load: under the conditions above set forth.

A further object of the invention is to provide a new and improved grip type arm capable of supporting heavy loads in shear.

Another object of the invention is to provide a new and improved grip type load arm having an improved load engaging element which may be inexpensively 'manufactured and easily and rapidly replaced in a load arm in case of damage thereto.

Another object of the invention is to provideA a grip type load arm which is adapted to confor-m. readily to irregularities in a load surface, and to apply a substantially equal pressure over the entire engaged surface.

A still further object of the invention is to provide a simple, rugged grip type load engaging device which may be easily manufactured and which requires little or no maintenance after installation.

Another object of the invention isr to provide anew and improved, hydraulically biased grip type lift arm.

@ther objects and advantagesof the invention will become apparent hereinafter'.

The load arm of the present invention ischaracterized by including a rigid receptacle and a load engaging` means or device arranged within said receptacle and including relatively movable load contacting members or parts projecting from the receptacle for engaging a load. T he load engaging means includes a cavity t-o ber lled withl fluid, the cavity being disposed behind the load contacting mem- 2,768,018 Patented Oct. 23, 1956 ICC 2 bers or parts and being wholly disposed within the receptacle. The load contacting members or parts project from the receptacle by la distance greater than the thickness of the cavity so that the load contacting members will remain in projecting relationship with respect to the receptacle in the event fof collapse of the cavity or bottoming of said members.

For a .more detailed description ofthe invention, reference is made to the following specification taken in connection with the accompanying drawing, wherein:

Fig. 1 is a perspective View of an industrial lift truck having the lift arms of the invention mounted thereon;

Fig. 2 is a front view of the lift truck showingl the manner in which a stack of bricks is engaged and lifted by the lift arms;

Fig. 3 is a side elevation of the lift arm of the invention;

Fig. 4 is a section along, line 4 4 of Fig. 3;

Fig. 5 is a section along line 5 5 of Fig. 6;A and Fig. 6 is a bott-om plan View, partially in section, of the lift arm of Fig.. 3 showing the action thereof in engaging an irregular load surface.

Although the lifting arms of the subject invention are adapted for use with various typen of lifting mechanisms, the industrial li'ft truck is one type of conveyance to which the present invention is well suited, and in connection with which the invention will be described. Such a truck is shown in Fig. l and indicated generally by the reference numeral 10 and having a load lifting mechanism including an upright' stnicture 11 on thev forward end thereof.

Mounted. on the upright 11, and adapted for vertical movement therealong, is av load carriage 22. Projecting forwardly from the carriage 22 is a pair of load lifting arm assemblies 25, 26,.the arm assemblies being supported upon the carriage. for relative movement toward and away from each other by suitable lmeans such as by hydraulic cylinder and piston means 27 whereby they are adapted to grip a load therebetween preparatory to lifting the same. Reference may be made to United States Patent 2,571,550, or the reissue thereof, 23,694, for a disclosure of one manner of moving the arms toward and away from one another.

The lift arm assemblies shown on the truck of Fig. l are essentially similar to each other, and the detailed views :of Figs. 3, 4, 5 andV 6, therefore, illustrate a single arm assembly. Each `of the. arm assemblies 25, 26 includes an elongated supporting member 29 formed of steel or other rigid metal, having a vertically disposed web 30 and a pair of oppositely disposed, horizontally extending flange portions 31, 32 defining a channel or receptacle of substantially .rectangular cross-section facing the other arm. The arm ilanges 31, 32 and the web 30 are welded at their rearward ends to an arm mounting plate 33, the plate 33 being 'suitably mounted upon the carriage 22 and attached to the hydraulic cylinder and piston. means 27 for movement thereby. The forward end of the arm channel is closed with an integral end piece 34 whereby the arm in effect defines a boxlike structure open on one elongated side thereof. Extending from the arm web 30 in a direction opposite to that. `of the, flanges 31, 32 is a pair of oppositely disposed bracing anges 36 which increase in depth from front to rear of the arm.

Mounted snugly within the channel of the member 29 between the flanges 31, 32 is a load engaging means or device which is shown, in the particular embodiment of the invention illustrated, as comprising a substantially rectangular, unitary, elongated, hollow load gripping elementl 37 formed of rubber or other resilient, rubberlike material 4and including a rear wa'll `or base portion 38 fitting against the arm web 3b and a relatively thick forward or front wall lo-ad contacting port-ionV 39 spaced from the base portion and projecting a. predetermined distance beyond the longitudinal forward edges 43 of the arm flanges. The base portion 38, the forward wall portion 39 and the pair of relatively thin, flexible side Walls 41, 42 extending therebetween adjacent the flanges 31, 32, respectively, define a cavity 40 which extends substantially the full length and full width `of the load gripping element 37 and which is completely filled with hydraulic brake fluid lor any other suitable liquid. The depth of the cavity 40 in a direction at right angles to the plane of the web 30 of the arm is such that the cavity is wholly within the confines of the arm, and preferably the cavity 40 is spaced so that in the normal operation of the larm the forward wall thereof, defined by the forward wall portion 39, is a substantial distance rearwardly of the forward, longitudinal flange edges 43, whereby the flanges 31, 32 overlap the forward wall portion 39 by a distance approximately equal to the normal depth of the cavity. Preferably the forward wall portion 39 extends beyond the liange edges 43 by a distance greater than the depth of the cavity, the |reasons for the foregoing construction being described more fully hereinafter.

In lorder that the forward wall portion 39 may more readily deform to meet irregularities in a load surface, it is preferably articulated by providing a plurality of deep, relatively widely spaced apart, transversely extending grooves 45 in the face thereof, which grooves divide the section into a plurality of thick, stiff, rectangular sections or blocks 46 joined by relatively narrow, thin, flexible wall sections 47 adjacent the cavity 40. As will be apparent from Fig. 6, wherein the anm is shown in contact with an irregular row of bricks 54, the projecting portions of a load surface will cause the blocks 46 engaged thereby to be depressed inwardly a greater distance than the remaining blocks. Since the cavity is sealed and completely filled with a liquid, the liquid displaced by an inwardly depressed block must cause an expansion of the cavity at some other point. The distention of the cavity walls to accommodate this expansion can only take place outwardly of the open side -of the arm member 29 inasmuch as the rear and side walls =of the load engaging element 37 are restrained from distending by the web and anges of the arm member 29. Thus the blocks 46 which are not engaged by the projecting portions of 'a load surface will be forced outwardly into contact with the depressions at other points thereon. It should be noted, however, that since the blocks are biased by a Iliquid, a substantially equal pressure will be applied to the load surface by each block regardless of the condition yof alignment.

Provided within the cavity 40 adjacent the rear wall thereof, and extending substantially the full width and length of the cavity, is a clamping plate 48. Welded to the plate 48 and extending through cooperative openings in the base portion 38 and web 3) is a plurality of -anchoring studs 49 engaged by nuts St) to draw the plate toward the web and hold the element 37 securely in place. With the clamping plate 48 extending the full width and length of the cavity, any tendency for the load gripping element 37 to peel away from the arm web 30 by reason of the'vertical component of a load as represented by the arrow V in Fig. 5, will be substantially eliminated.

To facilitate filling the cavity 40 with liquid, one `of the clamping plate mounting studs 49 (Fig. 6) may be provided with a longitudinally extending bore S1 which communieates with the cavity 40. After the cavity has been completely lilled with liquid, the bore may be sealed by suitable means such as a `screw plug 52 fitting cooperatively therein.

In forming a load gripping element 37, the clamping plate 48 with studs 49 already secured thereto may be placed within a mold and a suitable core placed upon the upper surface of the clamping plate. The cone can be made to extend short of one end wall of the mold, but

to extend to or through the other end wall of the mold. A

4 studs 49, and thereafter the core can be removed yand the open end of the gripping element vulcanized closed.

It has been previously mentioned that the arm is preferably designed so that the forward wall portion 39 extends rearwardly of the flange edges 43 a substantial distance and forwardly thereof by a distance greater than the depth of the cavity 40. By reason of the latter feature, in the event of complete collapse of the cavity at a point therealong, or in the event `of bottoming of (me or more of the blocks 46, the part of the forward wall portion opposite the collapsed point will still project beyond the arm flanges and retain gripping contact with the iload engaged by the arm. It is desirable, on the other hand, that a substantial part of the forward wall portion 39 be spaced rearwardly of the flange edges 43 so that the lower arm flange 32 will firmly support the forward wall portion when a heavy load is engaged thereby, and also so that the possibility of a portion of the cavity distending beyond the ange edges 43 is minimized, which, if it occurred, would free the cavity side walls 41, 42 of the restraint afforded by the arm flanges 31, 32 permitting them to expand with the consequent loss of biasing pres sure on the engaged blocks 46.

Though lifting arms of the type described are useful for picking up objects of many types, a particularly useful application is illustrated in Fig. 2 wherein a stack of bricks is shown with the lower course 55 gripped between the load arms 25, 26 and supporting the upper layers 56. The overhanging arrangement yof the brick stack permits stacks to be placed closely adjacent each other, whereas the channels between the bottom courses of the adjacent stacks will provide room for insertion of the gripping arms 25, 26.

It will be seen that the load engaging arm assembly of the present invention may be easily and inexpensively manufactured and that it can be easily installed or interchanged on existing grip type load handling devices, since the arm assembly is a complete unit within itself. The load gripping element 37 may, moreover, be readily and quickly replaced should it become damaged or worn.

Having illustrated and described a preferred embodiment of the invention, it should be apparent to those skilled in the `art that the invention permits of modification in arrangement and detail. I claim as my invention all such modifications as come within the true spirit and scope of the appended claims.

I claim:

l. An arm for a load handling apparatus of the type described, comprising a receptacle, a load engaging element of a resilient, rubberlike material including a base portion mounted within said receptacle and a `forward wall portion projecting outwardly from said receptacle, said element having a sealed, fluid filled cavity between said base and forward wall portions, said cavity being wholly disposed within said receptacle, said forward wall portion projecting from said receptacle by a distance greater than the normal depth of said cavity between said base and forward wall portions whereby said forward wall portion will extend beyond the edge of said receptacle in the event of complete collapse of said cavity at any point therealong.

2. An arm for a load handling apparatus of the type described, comprising an elongated rigid boxlike receptacle of shallow depth as compared to its length, a load engaging means snugly fitting within said receptacle and having independently movable block-shaped load engaging portions projecting from said receptacle for engag ing a load, said load engaging means having resilient wall portions defining a sealed liquid-lled cavity behind said block-shaped portions, said cavity being wholly disposed within said receptacle, said block-shaped portions projecting from said receptacle by a distance greater than the normal thickness of said cavity so that said block- .shaped portions will remain in projecting relationship with respect to said receptacle and thus in engagement with a load in the event of complete collapse of said cavity at any point therealong whereby a load or a part thereof will not be dropped under such conditions.

3. An arm for a load handling apparatus of the type described, comprising a rigid receptacle, load engagingl means arranged within said receptacle and including rela,- tively movabie load contacting members projecting from said receptacle for engaging a load, said load engaging means also including resilient wall portions defining a cavity to be tilted with iluid, said cavity being disposed behind said load contacting members and being wholly' disposed Within said receptacle, said load contacting members projecting from said receptacle by a distance greater than the thickness of said cavity so that said load contacting members will remain in projecting relationship with respect to said receptacle in the event of bottoniing oi said members.

4. An arm for a load handling apparatus of the type described, comprising a rigid receptacle, a load engaging device fitting and held Within said receptacle and including relatively movable load contacting parts projecting from said receptacle for engaging a load, said load engaging device defining a fluid lled cavity bounded by resilient Walls, said fluid filled cavity being disposed behind said load contacting parts in motion transmitting relation with respect thereto and being wholly disposed within said receptacle, said load contacting parts projecting from said receptacle by a distance greater than the thickness ot said cavity so that a load contacting part will remain in projecting relationship with respect to said receptacle in the event of bottorning of said part and thus remain in engagement with a load.

5. An arm assembly for a load handling apparatus of the type described, comprising a rigid receptacle, relatively movable load contacting members disposed within said receptacle and projecting from said receptacle for engaging a load, said assembly including resilient wall portions defining a cavity to be tilled with uid, said `cavity being disposed behind said load contacting members and being wholly disposed within said receptacle, said load contacting members projecting from said receptacle by a distance greater than the thickness of said cavity so that said load contacting members will remain in projecting relationship with respect to said receptacle in the event of bottoming of said members.

References Cited in the le of this patent UNITED STATES PATENTS 1,477,686 Braenoer Dec. 18, 1923 1,561,184 Offenhauser NOV. 10, 1925 1,602,719 Straight Oct. 12, 1926 2,211,499 Fontaine Aug. 13, 1940 2,247,168 Fontaine `lune 24, 1941 2,395,556 Kopplin Feb. 26, 1946 2,493,356 Francis July 2, 1946 2,416,575 Fontaine Feb. 25, 1947 2,557,394 Schmidgall June 19, 1951 2,571,550 Ehmann Oct. 16, 1951 2,539,101 Leguillon et al Mar. 11, 1952 2,609,113 Huffman Sept, 2, 1952 FOREIGN PATENTS 315,986 Great Britain July 25, 1929 633,180 Great Britain Dec. 12, 1949 

